WO2010135444A2

WO2010135444A2 - Simultaneous sample modification and monitoring

Info

Publication number: WO2010135444A2
Application number: PCT/US2010/035433
Authority: WO
Inventors: Rainer Knippelmeyer; Colin A. Sanford; Lawrence Scipioni; William B. Thompson
Original assignee: Carl Zeiss Nts, Llc
Priority date: 2009-05-20
Filing date: 2010-05-19
Publication date: 2010-11-25
Also published as: WO2010135444A3

Abstract

Systems (100, 200) and methods for simultaneously modifying a sample (154) and monitoring sample modification. In some embodiments, a single charged particle beam (122) is used to simultaneously monitor and modify the sample. In certain embodiments, one charged particle beam is used to monitor the sample while a different charged particle beam (132) is used to simultaneously modify the sample.

Description

SIMULTANEOUS SAMPLE MODIFICATION AND MONITORING

Field

The disclosure relates to systems and methods for simultaneously modifying a sample and monitoring sample modification.

Background

Ion microscope systems can be used to produce ions that are used, for example, to image a semiconductor sample, obtain chemical information about a semiconductor sample, and/or perform chemistry on a semiconductor sample. Microscope systems that use a gas field ion source to generate ions that can be used in sample analysis (e.g., imaging) are referred to as gas field ion microscopes. A gas field ion source generally includes a tip (typically having an apex with 10 or fewer atoms) that can be used to ionize neutral gas species to generate ions (e.g., in the form of an ion beam) by bringing the neutral gas species into the vicinity of the electrically conductive tip (e.g., within a distance of about four to five angstroms) while applying a high positive potential (e.g., one kV or more relative to the extractor) to the apex of the tip.

Summary

In general, the disclosure relates to systems and methods that allow an operator to modify a sample (e.g., a semiconductor sample) while simultaneously monitoring the sample. In some embodiments, the methods can be performed without interrupting sample modification to inspect the sample. Such systems and methods can provide enhanced precision of sample modification, while at the same time reducing the cost and/or complexity associated with sample modification. In certain embodiments, the methods can avoid issues (e.g., undesirably slow sample processing, sample contamination, sample misalignment) that can be associated with interrupting sample modification to determine the status of sample modification. Additionally or alternatively, the methods do not involve estimating the status of sample modification based on, for example, processing parameters, such as processing time, charged particle flux and/or gas pressure. Such methods can provide enhanced precision of sample modification, while also reducing the cost and/or complexity associated with sample modification, because the methods can avoid problems (e.g., excess sample sputtering, excess material deposition on the sample, excess chemical etching) that can be involved with estimating the status of sample modification.

In some embodiments, the systems and methods involve using a single charged particle beam to simultaneously modify and monitor the sample. As an example, the charged particle beam can be an ion beam generated by a gas field ion source. In such embodiments, for example, ions (e.g., scattered ions, secondary ions, neutral particles) generated by the interaction of the ion beam with the sample can be detected. Information regarding the detected charged particles (e.g., detected ions, detected neutral particles) can be used to provide, for example, qualitative and/or quantitative information about one or more chemical constituents of the sample. As another example, the charged particle beam can be an electron beam generated by an electron source, such as an electron microscope. In such embodiments, for example, electrons (e.g., Auger electrons) generated by the interaction of the electron beam with the sample can be used to determine information about one or more chemical constituents of the sample.

In certain embodiments, two different charged particle beams can be used. In such embodiments, the first charged particle beam can generally be an electron beam or an ion beam (e.g., a focused ion beam, an electron beam), which is used to modify the sample (e.g., to sputter the sample, to chemical etch the sample via gas assisted etching, and/or deposit material on the sample via gas assisted deposition), and the second charged particle beam is an ion beam (e.g., an ion beam generated by a gas field ion source), which is used to monitor the portion of the sample that is being modified. Typically, such embodiments involve detection of ions (e.g., scattered ions, secondary ions) generated by the interaction of the sample with ions in the second charged particle beam (which is an ion beam). Information regarding the detected ions can be used to provide qualitative and/or quantitative information about the sample.

In general, the interaction of the sample with the charged particle beam used to monitor the sample generates particles (e.g., electrons, ions). These particles can be detected, and the resulting information can be processed to provide information about the sample. This information can relate to the presence, absence and/or amount of one or more chemical constituents present at the portion of the sample that is being monitored. In some embodiments, in addition to or as an alternative to obtaining information regarding the chemical constituents of a sample, the information obtained about the sample can be topographical information, voltage contrast information, crystalline orientation, sub-surface information, optical properties, and/or magnetic properties.

In one aspect, the disclosure generally provides a method that includes using a charged particle beam to modify a portion of a sample, and simultaneously using the charged particle beam to monitor the portion of the sample.

In another aspect, the disclosure generally provides a method that includes using an ion beam to modify a portion of a semiconductor sample, and simultaneously detecting ions and/or neutral particles formed by the interaction of the ion beam with the semiconductor sample. The method also includes using the detected ions to determine one or more chemical constituents of the portion of the semiconductor sample. The ion beam is generated by a gas field ion source.

In a further aspect, the disclosure generally provides a method that includes using an electron beam to modify a portion of a sample, and simultaneously detecting Auger electrons formed by the interaction of the electron beam with the portion of the sample. The method also includes using the detected Auger electrons to determine one or more chemical constituents of the portion of the sample.

In an additional aspect, the disclosure generally provides a method that includes using a first charged particle beam to modify a portion of a sample, and simultaneously using a first ion beam to monitor the portion of the sample, where the first ion beam is different from the first charged particle beam. The method also includes detecting ions generated by the interaction of the first ion beam with the sample, and using the detected ions to determine one or more chemical constituents of the portion of the sample.

Other features and advantages of the disclosure will be apparent from the description, drawings, and claims.

Brief Description of the Drawings

Fig. 1 is a schematic representation of a system having a gas field ion source; and Fig. 2 is a schematic representation of a system having a gas field ion source and a focused ion beam source. Detailed Description

Semiconductor fabrication typically involves the preparation of an article (a semiconductor sample) that includes multiple layers of materials sequentially deposited and processed to form an integrated electronic circuit, an integrated circuit element, and/or a different microelectronic device. Such articles typically contain various features (e.g., circuit lines formed of electrically conductive material, wells filled with electrically non-conductive material, regions formed of electrically semiconductive material) that are precisely positioned with respect to each other (e.g., generally on the scale of within a few nanometers). The location, size (length, width, depth), composition (chemical composition) and related properties (conductivity, crystalline orientation, magnetic properties) of a given feature can have an important impact on the performance of the article. For example, in certain instances, if one or more of these parameters is outside an appropriate range, the article may be rejected because it cannot function as desired. As a result, it is generally desirable to have very good control over each step during semiconductor fabrication, and it would be advantageous to have a tool that could monitor the fabrication of a semiconductor sample at various steps in the fabrication process to investigate the location, size, composition and related properties of one or more features at various stages of the semiconductor fabrication process. As used herein, the term semiconductor sample refers to an integrated electronic circuit, an integrated circuit element, a microelectronic device or an article formed during the process of fabricating an integrated electronic circuit, an integrated circuit element, a microelectronic device. A semiconductor sample can be, for example, a portion of a flat panel display or a photovoltaic cell.

Regions of a semiconductor sample can be formed of different types of material (electrically conductive, electrically non-conductive, electrically semiconductive). Exemplary electrically conductive materials include metals, such as aluminum, chromium, nickel, tantalum, titanium, tungsten, and alloys including one or more of these metals (e.g., aluminum-copper alloys). Metal suicides (e.g., nickel suicides, tantalum suicides) can also be electrically conductive. Exemplary electrically non-conductive materials include borides, carbides, nitrides, oxides, phosphides, and sulfides of one or more of the metals (e.g., tantalum borides, tantalum germaniums, tantalum nitrides, tantalum silicon nitrides, and titanium nitrides). Exemplary electrically semiconductive materials include silicon, germanium and gallium arsenide. Optionally, an electrically semiconductive material can be doped (p-doped, n-doped) to enhance the electrical conductivity of the material.

Typical steps in the deposition/processing of a given layer of material include imaging the article (e.g., to determine where a desired feature to be formed should be located), depositing an appropriate material (e.g., an electrically conductive material, an electrically semiconductive material, an electrically non-conductive material) and etching to remove unwanted material from certain locations in the article. Often, a photoresist, such as a polymer photoresist, is deposited/exposed to appropriate radiation/selectively etched to assist in controlling the location and size of a given feature. Typically, the photoresist is removed in one or more subsequent process steps, and, in general, the final semiconductor sample desirably does not contain an appreciable amount of photoresist.

It is often desirable to modify a semiconductor sample. As an example, it can be desirable to modify a sample to expose a cross-section of a semiconductor sample (e.g., by etching and/or sputtering), and to inspect the cross-section. As another example, it can be desirable to edit one or more circuits of a semiconductor sample (e.g., by etching, sputtering and/or depositing material). As a further example, it can be desirable to repair one or more defects of a semiconductor sample (e.g., by etching, sputtering and/or depositing material). In some embodiments, it may be desirable to perform various combinations of these activities.

Fig. 1 shows a system 100 that includes having a housing 110 that contains a gas field ion source (GFIS) 120, a detector 140, a sample holder 150 and a semiconductor sample 154. During operation of system 100, source 120 generates an ion beam 122, and ions (e.g., helium (He) ions) in ion beam 122 impinge on a portion 152 of sample 154 to modify sample 154. Examples of sample modification include sputtering sample 154, chemically etching sample 154, depositing material on sample 154, or combinations thereof. Simultaneously, ions in an ion beam 122 impinge on the same portion 152 of sample 154, resulting in the generation of particles (e.g., scattered ions, secondary ions) that are detected by detector 140. Information regarding the detected particles is processed to provide information regarding sample 154. In some embodiments, such information relates to qualitative and/or quantitative information about chemical constituents present at portion 152 of sample 154. In certain embodiments, such as when ion beam 122 is used to sputter sample 154, relatively heavy ions (e.g., Neon (Ne) ions, Krypton (Kr) ions, Xenon (Xe) ions) can be used. In some embodiments, system 100 can be used to deposit material on a portion of semiconductor sample 154 while simultaneously monitoring one or more chemical constituents of the same portion of semiconductor sample 154. For example, ions in ion beam 122 and/or electrons (e.g., secondary electrons) generated by the interaction of sample 154 with ions in ion beam 122 can interact with an activating gas (e.g., WF₆) to deposit the desired material (e.g., tungsten (W)) on a portion of the semiconductor sample 154. Simultaneously, particles generated by the interaction of ions in ion beam 122 with the same portion of semiconductor sample 154 can be detected, and this information can be processed to provide information regarding one or more chemical constituents of the portion of the sample. As an example, the amount and/or concentration of the material being deposited (e.g., W) can be monitored. As the material (e.g., W) is deposited, the amount and of the material present at the portion of sample 154 being modified/monitored will increase. When the amount and/or concentration of the material being deposited reaches a certain level, the material deposition can be terminated As another example, the amount and/or concentration of a substrate material (e.g., silicon (Si)) can be monitored. As the material (e.g., W) is deposited on the portion of sample 154, the amount of the substrate material (e.g., Si) detected will decrease. When the amount and/or concentration of the substrate material (e.g., Si) reaches a certain level, material deposition can be terminated. Alternatively or additionally, during material deposition, the amount and/or concentration of one or more chemical constituents in one or more potential contaminants can be monitored. If the amount and/or concentration of a particular chemical constituent of a particular potential contaminant reaches a certain level, material deposition can be terminated.

In certain embodiments, system 100 can be used to etch a portion of semiconductor sample 154 while simultaneously monitoring one or more chemical constituents of the same portion of semiconductor sample 154. For example, ions in ion beam 122 and/or electrons (e.g., secondary electrons) generated by the interaction of ions in ion beam 122 can interact with an activating gas (e.g., Cl₂, O₂, 1₂, XeF₂, F₂, CF₄, H₂O) to etch the portion of semiconductor sample 154. Simultaneously, particles generated by the interaction of ions in ion beam 122 with semiconductor sample 154 can be detected, and this information can be processed to provide information regarding one or more chemical constituents of the portion of the sample. As an example, the amount and/or concentration of a material being etched (e.g., Si) can be monitored. As the portion of semiconductor sample 154 is etched, the amount and of the material (e.g., Si) will decrease. When the amount and/or concentration of the material (e.g., Si) being etched reaches a certain level, etching can be terminated. As another example, the amount and/or concentration of a material present in an underlying layer can be monitored. In some embodiments, the underlying layer can be formed of an etch stop material, and the amount and/or concentration of one or more chemical constituent of the etch stop material (e.g., Si, nitrogen (N), carbon (C), oxygen (O)) can be monitored. As etching occurs, the amount of the material that forms the underlying layer (e.g., etch stop material) will increase. When the amount and/or concentration of one or more constituents of the underlying layer reaches a certain level, etching can be terminated. Alternatively or additionally, during material deposition, the amount and/or concentration of one or more components of the activating gas can be monitored (e.g., using secondary ion spectroscopy; see discussion below), and this information can be used to indirectly determine whether etching should be terminated. For example, if a certain underlying layer is reached by etching, it may be the case that no further gas activated etching may occur, in which case the amount and/or concentration of the activating gas may increase, indicating that etching can be (or already has) terminated.

In some embodiments, system 100 can be used to sputter a portion of semiconductor sample 154 while simultaneously monitoring one or more chemical constituents of the same portion of semiconductor sample 154. For example, ions in ion beam 122 can sputter the portion of semiconductor sample 154. Simultaneously, particles generated by the interaction of ions in ion beam 122 with semiconductor sample 154 can be detected, and this information can be processed to provide information regarding one or more chemical constituents of the portion of the sample. As an example, the amount and/or concentration of a chemical constituent of the material being sputtered (e.g., Si, C, N, O, a metal, ) can be monitored. As the material is sputtered, the amount and/or concentration of the material present at the portion of the sample will decrease. When the amount and/or concentration of one or more chemical constituents of the material being sputtered reaches a certain level, sputtering can be terminated. As another example, the amount and/or concentration of a material present in an underlying layer can be monitored as sample 154 is sputtered. In some embodiments, the underlying layer may contain one or more metals (e.g., (e.g., a metal, W, copper (Cu), silver (Ag) or Gold (Au)), and the amount and/or concentration of one or more of the metals can be monitored. In certain embodiments, the underlying layer may contain certain other chemical constituents (e.g., Si, O, C, N), and the amount and/or concentration of one or more of these chemical constituents can be monitored. As sputtering occurs, the amount of the material that forms the underlying layer will increase. When the amount and/or concentration of one or more constituents of the underlying layer reaches a certain level, sputtering can be terminated.

As noted above, the interaction of the ions in ion beam 122 with semiconductor sample 154 generates certain particles. Such particles include secondary electrons, Auger electrons, secondary ions, secondary neutral particles, primary neutral particles, scattered ions and photons (e.g., X-ray photons, IR photons, visible photons, UV photons). These particles can be detected using one or more appropriate detectors, and used to provide certain information (e.g., chemical constituent information) about a portion of sample 154 being monitored. Exemplary GFIS components, systems and methods are disclosed, for example, in US Published Patent Application 2007-0158558, USSN 61/074,387 and USSN 61/092,919, which are incorporated by reference herein in their entirety.

In some embodiments, detector 140 detects scattered ions formed by the interaction of ion beam 122 with semiconductor sample 154. As referred to herein, a scattered ion is generated when an ion from an ion beam (e.g., a He ion) interacts with the sample and is scattered from the sample while remaining an ion (e.g., a He ion).

In certain embodiments, the total abundance of scattered ions can be used to determine qualitative material constituent information because, in general, the scattering probability of an ion , such as a He ion, (and therefore the total abundance of scattered ions, assuming no effects from other factors, such as topographical changes in the surface sample) is approximately proportional to the square of the atomic number (Z value) of the surface atom from which the ion scatters. Thus, as an example, when using He ions and trying to distinguish Cu (atomic number 29) from Si (atomic number 14) in a semiconductor sample, the total abundance of scattered He ions from a Cu atom at a surface of the semiconductor sample will be approximately four times the total abundance of scattered ions from a Si atom at the surface of the semiconductor sample. As another example, when using He ions trying to distinguish a W (atomic number 74) plug from Si (atomic number 14) in a semiconductor sample, the total abundance of scattered He ions from a W atom at a surface of the semiconductor sample will be approximately 25 times the total abundance of scattered ions from a Si atom at the surface of the semiconductor sample. As a further example, when using He ions trying to distinguish Au (atomic number 79) region from Si (atomic number 14) in a semiconductor sample, the total abundance of scattered He ions from a Au atom at a surface of the semiconductor sample will be approximately 25 times the total abundance of scattered ions from a Si atom at the surface of the semiconductor sample. As an additional example, when using He ions and trying to distinguish In (atomic number 49) from Si (atomic number 14) in a semiconductor sample, the total abundance of scattered He ions from an In atom at a surface of the semiconductor sample will be approximately 10 times the total abundance of scattered ions from a Si atom at the surface of the semiconductor sample. The total abundance of scattered ions can be detected using a single detector (e.g., a hemispherical detector) configured to detect scattered ions leaving the surface of a sample, or multiple detectors (e.g., located at different solid angles with respect to the surface of the sample) configured to detect scattered ions leaving the surface.

In some embodiments, energy-resolved and angle-resolved scattered ion detection can be used to determine quantitative material constituent information about the surface of a sample. The detector is designed so that the angle and energy of each detected scattered ion is known for each angle within the acceptance angle of detector. Using He ions as an example, by measuring the energy and scattering angle of the scattered He ion, the mass of the atom at the surface that scatters the scattered He ion can be calculated based on the following relationship:

£ _{= 1} 2M_HM (, _ )

where E_s is the energy of the scattered He ion, E₁ is the incident energy of the He ion, Mκ_e is the mass of the He ion, θ_s is the scattering angle, and M_a is the mass of the atom that scatters the He ion. The detector can, for example, be an energy-resolving phosphor-based detector, an energy- resolving scintillator-based detector, a solid state detector, an energy-resolving electrostatic prism-based detector, an electrostatic prism, an energy-resolving ET detector, or an energy- resolving microchannel. In general, it is desirable for the detector to have a substantial acceptance angle. In some embodiments, the detector is stationary (e.g., an annular detector). In certain embodiments, the detector can sweep through a range of solid angles. Although a system for detecting energy-resolved and angle-resolved scattered ions that includes a single detector has been described above, such a system can contain multiple (e.g., two, three, four, five, six, seven, eight) detectors. Often, the use of multiple detectors is desirable because it can allow for a larger acceptance angle of detected scattered ions. Optionally, information about scattered ions (e.g., peak height, peak width, position) can be compared to a standard to provide quantitative information about one or more chemical constituents of the sample.

As an example, W deposition can be monitored by tracking the growth of the backscattered He ion peak that appears at a maximum of 94% of the primary beam (beam 122) energy. The height of this peak can be matched to models that will give total area coverage, using a software package, such as, for example, SIMNRA. Alternatively or additionally, backscattered ions (e.g., backscattered He ions) can be used to monitor one or more chemical constituents present in deposited material (e.g., to monitor purity). This can be very useful information because the electrical and mechanical properties of the deposits generally depend on the purity of the deposition. Purity is traditionally determined after material deposition, but the relatively high surface sensitivity of the backscattered ion spectroscopy technique can allow relatively precise (and/or relatively low) levels of chemical constituents to be detected. This can be accomplished, for example, with software, such as SIMNRA, which can fit a composition profile.

As another example, the disappearance of the spectral edge for the etched material can be monitored. The etch process will lead to a shrinkage signal from the etched material peak. Since the backscattered ion signal is relatively highly localized, the backscattered ion peak can be assumed to come from just that area upon which the ion beam is being scanned to activate the etching. Fitting that peak height to determine the remaining layer thickness may provide monolayer precision. The limits to the monitoring process may depend on the lateral dimensions being etched, as well as the aspect ratio of the resulting hole in the sample.

In certain embodiments, detector 140 detects secondary ions formed by the interaction of ion beam 122 with sample 154. As referred to herein, a secondary ion is an ion formed when an ion beam interacts with the sample to remove a mono-atomic or poly-atomic species from the sample in a charged state. Interactions between an incident ion beam and the sample can produce secondary ions.

Detection of secondary ions from the sample can provide material constituent information about the sample via calculation of the masses of detected particles. In general, this information will correspond to material at the surface of the sample. In some embodiments, the mass(es) of the secondary ions is(are) determined using a combination of time -of- flight and a mass-resolved detector, such as a quadrupole mass spectrometer. Such secondary ion detection can be performed as follows. The ion beam is operated in pulsed mode by changing the electrical potentials applied to ion optical elements in the ion optics. Pulses of incident ions are incident on a surface of the sample. A clock signal, which determines the rate at which the ion optical element potentials are switched to turn the ion beam on and off, is also used as a reference time signal for the detector (see discussion above regarding detectors). In this manner, the time of flight of secondary ions from the sample to the detector can be accurately determined. Based upon a detected secondary ions' time of flight, its distance traveled (e.g., the distance between the detector and the sample), and its energy, the mass of the particle can be calculated, and the type of chemical species (e.g., atom) can be identified. This information is used to determine material constituent information for the sample. Secondary ion imaging techniques can be applied to a variety of different classes of samples. An example of such a class of materials is semiconductor samples, such as patterned wafers, which can include, for example, multiple electrical conductors surrounded by a matrix of insulating material. Secondary ion imaging techniques can be used to identify defects in the device, such as incomplete electrical connections between conductors, and/or electrical shorts between circuit elements. Optionally, this approach can similarly be used for purposes of mask repair. Another example of a sample class for which secondary ion imaging techniques can be used is metals and alloys. For example, images of samples that contain mixed materials such as alloys can be used to determine the surface distribution of each of the materials in the sample. Yet another example of a sample class where secondary ion imaging techniques can be used is read/write structures for data storage. Additional examples of classes of materials for which secondary ion imaging techniques can be used are biological materials and pharmaceutical materials.

In some embodiments, secondary ion mass spectrometry can be used to monitor/detect one or more volatized reaction products. For example, when etching, this signal can indicate when an interface is reached because the substrate material will change, which can be detected as a change in the secondary ion signal. As another example, when depositing material, the secondary ion signal may include fragments of molecules that composed one or more deposition precursors. The abundance of these fragments could serve as an indirect indicator of total deposited mass and/or layer thickness. In certain embodiments, detector 140 detects neutral particles (primary neutral particles, secondary neutral particles) formed by the interaction of ion beam 122 with sample 154. As referred to herein, a primary neutral particle is a neutral particle generated when ion beam 122 interacts with sample 154 and an ion (e.g., a He ion) from ion beam 122 leaves sample 154 as an un-charged neutral particle (e.g., an un-charged He atom). A secondary neutral particle is a neutral particle generated when ion beam 122 interacts with sample 154 to remove a mono- atomic or poly-atomic species from sample 154 in an un-charged state. Interactions between ion beam 122 and sample 154 can produce secondary neutral particles. Typically, this method is more effective when using a noble gas ion of mass greater than He (Ar ions, Ne ions, Kr ions, Xe ions). In general, to access the information available from secondary neutral particles, the particles are ionized (e.g., via laser induced ionization, electron induced ionization) prior to detection.

In contrast to scattered He ions, primary He atoms are a relatively sensitive probe of the sub-surface region of a sample. As used herein, the sub-surface region is the region of a sample that is more than five nm beneath the sample surface (e.g., 10 nm or more beneath the sample surface, 25 nm or more beneath the sample surface, 50 nm or more beneath the sample surface), and 1000 nm or less beneath the sample surface (e.g., 500 nm or less beneath the sample surface, 250 nm or less beneath the sample surface, 100 nm or less beneath the sample surface). In general, the probe depth of the ion beam increases as the energy of the ions increase. Thus, to determine deeper sub-surface information about a sample, a higher energy ion beam can be used. A depth profile of material constituent information can be obtained by taking multiple He atom images of a sample at varying ion beam energies (probe depths). In some embodiments, tomographic reconstruction algorithms and/or techniques can be applied to the depth dependent information to perform tomographic reconstruction of the structure of the sample. In general, material constituent information based on the detection of primary He atoms can be determined using total abundance detection, energy-resolved/angle-resolved detection, or both, using detector arrangements as described above with respect to the corresponding techniques for scattered He ions and also using the same mathematical relationships as described above for scattered He ions. Typically, however, the detector(s) used for primary He atoms is capable of detecting a neutral species. Examples of such detectors include microchannel plates, channeltrons and scintillator/PMT detectors. Primary neutral particle (e.g., He atom) techniques can be applied to a variety of different classes of samples. An example of such a class of materials is semiconductor articles, such as patterned wafers, which can include, for example, multiple electrical conductors surrounded by a matrix of insulating material. Primary neutral particle techniques can be used to identify defects in the device, such as incomplete electrical connections between conductors, and/or electrical shorts between circuit elements. Optionally, this approach can similarly be used for purposes of mask repair. Another example of a sample class for which primary neutral particle imaging techniques can be used is metals and alloys. For example, images of samples that contain mixed materials such as alloys can be used to determine the surface distribution of each of the materials in the sample. Yet another example of a sample class where primary neutral particle imaging techniques can be used is read/write structures for data storage. Additional examples of classes of materials for which primary neutral particle imaging techniques can be used are biological materials and pharmaceutical materials.

Detection of secondary neutral particles (post-ionization) from the sample can provide material constituent information about the sample via calculation of the masses of detected particles. In general, this information will correspond to material at the surface of the sample. In some embodiments, the mass(es) of the secondary neutral particles (post-ionization) is(are) determined using a combination of time-of-flight and a mass-resolved detector, such as a quadrupole mass spectrometer. Such secondary neutral particle (post-ionization) detection can be performed as follows. The ion beam is operated in pulsed mode by changing the electrical potentials applied to ion optical elements in the ion optics. Pulses of incident ions are incident on a surface of the sample. A clock signal which determines the rate at which the ionization device (e.g., laser, electron beam) and/or ion optical element potentials are switched is also used as a reference time signal for the detector (see discussion above regarding detectors). In this manner, the time of flight of secondary neutral particles (post ionization) from the sample to the detector can be accurately determined. Based upon a detected secondary ions' time of flight, its distance traveled (e.g., the distance between the detector and the sample), and its energy, the mass of the particle can be calculated, and the type chemical species (e.g., atom) can be identified. This information is used to determine material constituent information for the sample. Secondary neutral particle imaging techniques can be applied to a variety of different classes of samples. An example of such a class of materials is semiconductor articles, such as patterned wafers, which can include, for example, multiple electrical conductors surrounded by a matrix of insulating material. Secondary neutral particle imaging techniques can be used to identify defects in the device, such as incomplete electrical connections between conductors, and/or electrical shorts between circuit elements. Optionally, this approach can similarly be used for purposes of mask repair. Another example of a sample class for which secondary neutral particle imaging techniques can be used is metals and alloys. For example, images of samples that contain mixed materials such as alloys can be used to determine the surface distribution of each of the materials in the sample. Yet another example of a sample class where secondary neutral particle imaging techniques can be used is read/write structures for data storage. Additional examples of classes of materials for which secondary neutral particle imaging techniques can be used are biological materials and pharmaceutical materials.

Fig. 2 shows a system 200 having a housing 210 that contains GFIS 120, a focused ion beam (FIB) source 130, detector 140, sample holder 150 and semiconductor sample 154. During operation of system 100, ions in an ion beam 132 (e.g., a beam of gallium (Ga) ions) generated by FIB source 130 impinge on portion 152 of sample 154 to modify sample 154. Examples of such modification include sputtering sample 154, chemically etching sample 154, depositing material on sample 154, or combinations thereof. Such modification can occur in a fashion similar to that discussed above with regard to ion beam 122. Simultaneously, ions in ion beam 122 impinge on the same portion 152 of sample 154, resulting in the generation of particles (e.g., scattered ions, secondary ions) that are detected by detector 140. Information regarding the detected particles is processed to provide information regarding sample 154. Such information can be obtained in a fashion similar to that discussed above. In some embodiments, such information relates to qualitative and/or quantitative information about chemical constituents present at the portion of sample 154 upon which ion beam 122 impinges.

While certain embodiments have been described, other embodiments are possible.

As an example, while embodiments have been described in which an ion beam is used to modify a sample, in some embodiments, an electron beam can be used to modify the sample (e.g., etch, deposit material). In some embodiments, an electron beam (e.g., generated by an electron microscope) can interact with an activating gas (e.g., the electrons in the beam or electrons formed by the interaction of the electron beam with the sample) to etch a sample and/or to deposit material on the sample. As another example, while embodiments, have been described in which an ion beam generated by a gas field ion source is used to a sample, in some embodiments a different charged particle beam can be used to monitor the sample. For example, an electron beam (e.g., formed by an electron microscope) can be used to monitor the sample. In such embodiments, for example, Auger electrons can be detected to monitor the sample during sample modification. This can result in a signal that is relatively sensitive to the sample surface, and that can, for example, provide information about the thickness of a layer thickness (e.g., in the 5 nanometer to 10 nanometer range of film thickness). In some embodiments when the primary electron beam energy is held above the threshold for Auger emission, the process can be considered to be analogous to the backscattered ion detection method disclosed herein. In certain embodiments, the same electron beam is used to monitor the sample and to also modify the sample (e.g., in a fashion similar to that shown in Fig. 1, except that, rather than a GFIS that creates an ion beam, an electron source that creates an electron beam, such as an electron microscope, is used).

As a further example, while embodiments have been described in which information about one or more chemical constituents of a sample are monitored as the sample is modified, in some embodiments, other information about the sample can be obtained. Such information can include, for example, topographical information about the sample, voltage contrast information about the sample, crystalline orientation information about the sample, sub-surface information about the sample, optical properties of the sample, and/or magnetic properties of the sample. This information may obtained in addition to or instead of chemical constituent information about the sample. Examples of detectors that may be used, depending on the type(s) of particles to be detected, include Everhart-Thornley (ET) detectors, microchannel plate detectors, conversion plates, channeltron detectors, phosphor detectors and solid state detectors. The detectors can be used to detect one or more of the types of particles noted above. In some embodiments, a detector (e.g., a prism detector, a solid state detector) can be used to detect the energy of a particle (e.g., an electron, a scattered ion).

As an additional example, in certain embodiments, multiple charged particle beams (e.g., two charged particles beams, three charged particle beams, four charged particle beams, etc.) can be used to monitor a sample and/or multiple charged particle beams (e.g., two charged particles beams, three charged particle beams, four charged particle beams, etc.) can be used to modify a sample. The charged particle beams can be the same or different, and can be generated by the same or different sources or types of sources.

As a further example, while embodiments have been described in which one detector is used, in some embodiments multiple detectors can be used. The detectors can be used to detect the same type of particles or different types of particles. The detectors can be the same type of detectors or different types of detectors. Information from the particles detected by different detectors can be processed to provide similar information about a sample or different types of information about a sample.

As an additional example, while embodiments have been described in which a detector is located on the same side of a sample as one or more charged particle beam sources, in some embodiments, one or more detectors may be located on the opposite side of the sample from one or more charged particles. Such a detector may be used, for example, to detect a charged particle that passes through the sample.

As another example, while embodiments involving a semiconductor sample have been described, in some embodiments, a different type of sample can be modified and monitored. Examples of such samples include biological samples (e.g., tissue, nucleic acids, proteins, carbohydrates, lipids and cell membranes), pharmaceutical samples (e.g., a small molecule drug), frozen water (e.g., ice), read/write heads used in magnetic storage devices, and metal and alloy samples. In some embodiments, the sample can be a mask (e.g., a mask used in semiconductor micro lithography). In some embodiments, He ion microscopes can be used to identify and examine metal corrosion in various devices and material. For example, metal fixtures and devices used in nuclear power plants, military applications, and biomedical applications can undergo corrosion due to the harsh environments in which they are deployed. He ion microscopes can be used to construct images of these and other devices based on the relative abundance of hydrogen (H) in the devices, which serves as reliable indicator of corrosion. Typically, to construct images based on scattered H ions or atoms, a detector for these ions or atoms is positioned on the back side of a sample, opposite to an incident He ion beam. Exposing the sample to He ions generates scattered H atoms and ions from within the sample, and these scattered H atoms and ions can be detected and used to construct images of the sample. The H abundance images can then be used to assess the extent of corrosion within the sample. The small spot size and interaction volume of the He ion beam can result in high resolution H images of the sample to be obtained without damaging the sample. In certain embodiments, read/write heads used in magnetic storage devices such as hard disks are fabricated to extremely high tolerances and must be inspected for manufacturing defects prior to installation. These devices frequently have very high aspect ratios; the short sides of such devices can be as small as 1 nm. He ion microscopes provide numerous advantages when used to image these devices during inspection. Among these are small spot sizes and interaction volumes, which can result in high resolution imaging of these tiny devices, a large depth of focus, which can allow in-focus imaging of the entire high-aspect-ratio device along its long dimension, and material information provided by measurement of scattered He ions and/or neutral atoms, which is used to verify that tiny circuit elements are properly connected. In some embodiments, the systems and methods can determine elemental and/or chemical compositional information about a biological sample using a non-destructive technique. Examples of biological samples include tissue, nucleic acids, proteins, carbohydrates, lipids and cell membranes. A gas field ion microscope (e.g., a He ion microscope) as described herein can be used to determine, for example, topographical information about a biological sample, material constituent information of a surface of a biological sample, material constituent information about the sub-surface region of a biological sample and/or crystalline information about a biological sample. For example, the gas field ion microscope can be used to image immuno-labeled cells and internal cell structures. The microscope can be used in this manner while providing certain advantages disclosed herein. Often, a therapeutic agent (e.g., small molecule drug) will form as a crystal (e.g., as it comes out of solution). It can be desirable to determine the crystalline structure of the crystallized small molecule because this can, for example, provide information regarding the degree of hydration of the small molecule, which, in turn, can provide information regarding the bioavailability of the small molecule. In certain instances, the crystalline information may turn out to demonstrate that the small molecule is actually in an amorphous (as opposed to crystalline) form, which can also impact the bioavailability of the small molecule. Additionally or alternatively, it is often desirable to determine elemental and/or chemical compositional information about a biological sample using a non-destructive technique.

In general, various aspects of the foregoing embodiments can be combined as desired.

Other embodiments are covered by the claims.

Claims

Claims What is claimed is:

1. A method, comprising: using a charged particle beam to modify a portion of a sample; and simultaneously using the charged particle beam to monitor the portion of the sample.

2. The method of claim 1 , wherein the charged particle beam comprises an ion beam.

3. The method of claim 1 or 2, wherein the ion beam is generated via gas field ion source.

4. The method of one of the claims 1 - 3, wherein the method provides quantitative information about the one or more chemical constituents of the sample.

5. The method of one of the claims 1 - 4, wherein monitoring the sample comprises detecting ions generated by the interaction of the ion beam with the sample.

6. The method of one of the claims 1 - 5, wherein monitoring the sample comprises detecting neutral particles generated via the interaction of the charged particle beam with the portion of the sample.

7. A method, comprising: using an ion beam to modify a portion of a semiconductor sample; and simultaneously detecting ions and/or neutral particles formed by the interaction of the ion beam with the semiconductor sample; and using the detected ions and/or neutral particles to determine one or more chemical constituents of the portion of the semiconductor sample, wherein the ion beam is generated by a gas field ion source.

8. A method, comprising: using a first charged particle beam to modify a portion of a sample; and simultaneously using a first ion beam to monitor the portion of the sample, the first ion beam being different from the first charged particle beam; detecting ions generated by the interaction of the first ion beam with the sample; and using the detected ions to determine one or more chemical constituents of the portion of the sample.

9. The method of claim 8, wherein the first charged particle beam comprises a second ion beam.

10. The method of one of the claims 8 or 9, wherein the first ion beam is generated via a gas field ion source.

11. The method of one of the claims 5 - 10, wherein detecting ions comprises energy- resolved and angle-resolved scattered ion detection.

12. The method of one of claims 5 - 10, wherein a total abundance of scattered ions is determined.

13. The method of claim 1, wherein the charged particle beam comprises an electron beam, monitoring the portion of the sample comprises detecting electrons and wherein the detected electrons comprise Auger electrons.

14. The method of one of the claims 1 - 13, wherein modifying the portion of the sample comprises etching the portion of the sample or depositing material on the portion of the sample.

15. The method of claim 14, further comprising terminating etching the portion of the sample if a first chemical constituent of the sample is determined to be present at the portion of the sample above a first concentration.

16. The method of claim 14 further comprising terminating etching of the portion of the sample if a first chemical constituent is determined not to be present at the portion of the sample above a first concentration.

17 The method of one of the claims 5 - 12 or 14 - 16, wherein the detected ions are secondary ions, and wherein detecting the secondary ions comprise performing secondary ion mass spectrometry.

18. A method, comprising : using an electron beam to modify a portion of a sample; simultaneously detecting Auger electrons formed by the interaction of the electron beam with the portion of the sample; and using the detected Auger electrons to determine one or more chemical constituents of the portion of the sample.

19. The method of claim 18, further comprising terminating modification of the sample based on the detected Auger electrons.